1. Field of the Invention
The present invention relates to a terminal structure and a vacuum pump, and in particular, to a terminal structure capable of preventing damage due to an excessive force and having high sealing property, and a vacuum pump to which the terminal structure is applied.
2. Description of the Related Art
As a result of recent developments in electronics, there is a rapidly increasing demand for semiconductor devices such as memories and integrated circuits.
Such semiconductor devices are manufactured by doping semiconductor substrates of a very high purity with impurities to impart electrical properties thereto, by forming minute circuits on the semiconductor substrates through etching, etc.
In order to avoid the influences of dust in the air, etc., such operations must be conducted in a chamber in a high vacuum state. To evacuate this chamber, a vacuum pump is generally used; in particular, a turbo molecular pump, which is a kind of vacuum pump, is widely used since it allows maintenance with ease, etc.
Further, a semiconductor manufacturing process involves a number of steps of causing various process gasses to act on a semiconductor substrate, and the turbo molecular pump is used not only to create a vacuum in the chamber but also to evacuate such process gases from the chamber.
Further, in an equipment such as an electron microscope, a turbo molecular pump is used to create a high vacuum state within the chamber of the electron microscope, etc. in order to prevent refraction, etc. of the electron beam due to the presence of dust or the like.
Further, such a turbo molecular pump is composed of a turbo molecular pump main body for sucking gas from the chamber of a semiconductor manufacturing apparatus, the electron microscope, or the like, and a control device for controlling the turbo molecular pump main body.
FIG. 5 shows a longitudinal sectional view of the turbo molecular pump main body.
In FIG. 5, a turbo molecular pump main body 100 has an inlet port 101 formed at the upper end of an outer cylinder 127. On an inner side of the outer cylinder 127, there is provided a rotor 103 in a periphery of which there are formed radially and in a number of stages a plurality of rotary vanes 102a, 102b, 102c, . . . formed of turbine blades for sucking and evacuating gases.
Mounted at a center of this rotor 103 is a rotor shaft 113, which is levitatingly supported and position-controlled by, for example, a so-called 5-axis control magnetic bearing.
Upper radial electromagnets 104 are four electromagnets arranged in pairs in an X-axis and an Y-axis. In close proximity to and in correspondence with the upper radial electromagnets 104, there are provided four upper radial sensors 107. The upper radial sensors 107 detect radial displacement of the rotor 103, and transmit displacement signals to a control device 200.
Based on the displacement signals detected by the upper radial sensors 107, the control device 200 controls the excitation of the upper radial electromagnets 104 by an output of an amplifier transmitted through a magnetic bearing control circuit having a PID adjustment function, and adjusts the radial position of an upper side of the rotor shaft 113. Here, the magnetic bearing control circuit converts analog sensor signals representing the displacement of the rotor shaft 113 detected by the upper radial sensors 107 into digital signals by an A/D converter, and processes the signals to adjust electric current caused to flow through the upper radial electromagnets 104, levitating the rotor shaft 113.
Further, to perform fine adjustment on the electric current caused to flow through the upper radial electromagnets 104, the electric current caused to flow through the upper radial electromagnets 104 is measured, and fed back to the magnetic bearing control circuit.
The rotor shaft 113 is formed of a high magnetic permeability material (such as iron), and is attracted by the magnetic force of the upper radial electromagnets 104. Such adjustment is effected independently in the X-axis and the Y-axis directions.
Further, lower radial electromagnets 105 and lower radial sensors 108 are arranged in the same way as the upper radial electromagnets 104 and the upper radial sensors 107, and the lower radial position of the of the rotor shaft 113 is adjusted by the control device 200 in the same manner as the upper radial position thereof.
Further, axial electromagnets 106A and 106B are arranged so as to sandwich from above and below a circular metal disc 111 provided in a lower portion of the rotor shaft 113. The metal disc 111 is formed of a high magnetic-permeability material, such as iron. There are provided axial sensors 109 for detecting an axial displacement of the rotor shaft 113. Axial displacement signals obtained through detection by the axial sensors 109 are transmitted to the control device 200.
Based on the axial displacement signals, the axial electromagnets 106A and 106B are excited and controlled by the output of the amplifier transmitted through the magnetic bearing control circuit with a PID adjustment function of the control device 200. The axial electromagnets 106A attract the metal disc 111 upwards by the magnetic force, and the axial electromagnets 106B attract the metal disc 111 downwards.
In this way, the control device 200 appropriately adjusts the magnetic forces exerted on the metal disc 111 by the axial electromagnets 106A and 106B, and magnetically levitates the rotor shaft 113 in the axial direction, retaining it in the air in a non-contact fashion.
A motor 121 is equipped with a plurality of magnetic poles circumferentially arranged so as to surround the rotor shaft 113. Each of these magnetic poles is controlled so as to rotate and drive the motor 121 by a power signal output from a drive circuit and transmitted through a motor control circuit with a PWM control function of the control device 200.
Further, the motor 121 is equipped with an RPM sensor and a motor temperature detecting sensor (not shown) The RPM of the rotor shaft 113 is controlled by the control device 200 on the basis of detection signals received from the RPM sensor and the motor temperature detecting sensor.
There are arranged a plurality of stationary vanes 123a, 123b, 123c, . . . , with a slight gap being between them and the rotary vanes 102a, 102b, 102c, . . . , respectively. In order to downwardly transfer the molecules of the exhaust gas through collision, the rotary vanes 102a, 102b, 102c, . . . are inclined by a predetermined angle with respect to planes perpendicular to the axis of the rotor shaft 113.
Further, the stationary vanes 123 are inclined by a predetermined angle with respect to planes perpendicular to the axis of the rotor shaft 113, and are arranged so as to protrude toward the interior of the outer cylinder 127 and in alternate stages with the rotary vanes 102.
Further, one ends of the stationary vanes 123 are supported while being inserted between a plurality of stationary vane spacers 125a, 125b, 125c, . . . stacked together.
The stationary vane spacers 125 are ring-like members formed of a metal, such as aluminum, iron, stainless steel, or copper, or a metal such as an alloy containing those metals as the components.
Further, in an outer periphery of the stationary vane spacers 125, the outer cylinder 127 is fixed in position with a slight gap therebetween. A base portion 129 is provided at a bottom portion of the outer cylinder 127. Between the lower portion of the stationary vane spacers 125 and the base portion 129, there is provided a threaded spacer 131. In the portion of the base portion 129 which is below the threaded spacer 131, there is formed an exhaust port 133, which communicates with the exterior.
The threaded spacer 131 is a cylindrical member formed of a metal, such as aluminum, copper, stainless steel, or iron, or a metal such as an alloy containing those metals as the components, and has in an inner peripheral surface thereof a plurality of spiral thread grooves 131a formed.
The spiral direction of the thread grooves 131a is a direction in which, when the molecules of the exhaust gas move in the rotating direction of the rotor 103, these molecules are transferred toward the exhaust port 133.
In the lowermost portion of the rotor 103 connected to the rotary vanes 102a, 102b, 102c, . . . , there is provided a rotary vane 102d vertically downwards. The rotary vane 102d has an outer peripheral surface of a cylindrical shape, protrudes toward the inner peripheral surface of the threaded spacer 131, and is placed in close proximity to the threaded spacer 131 with a predetermined gap therebetween.
Further, the base portion 129 is a disc-like member constituting a base portion of the turbo molecular pump main body 100, and is generally formed of a metal, such as iron, aluminum, or stainless steel.
The base portion 129 physically retains the turbo molecular pump main body 100, and also functions as a heat conduction path, so it is desirable to use a metal that is rigid and of high heat conductivity, such as iron, aluminum, or copper, for the base portion 129.
Further, a connector 160 is arranged on the base portion 129. The connector 160 serves as an outlet for signal lines between the turbo molecular pump main body 100 and the control device 200. The turbo molecular pump main body 100 side portion of the connector 160 is formed as a male terminal and the control device 200 side portion thereof is formed as a female terminal. Further, the connector 160 has a seal structure, which is detachable, and capable of maintaining a vacuum inside the turbo molecular pump main body 100.
When, with this construction, the rotary vanes 102 are driven by the motor 121 and rotate together with the rotor shaft 113, an exhaust gas is sucked from a chamber through the inlet port 101 by the action of the rotary vanes 102 and the stationary vanes 123.
Then, the exhaust gas sucked in through the inlet port 101 flows between the rotary vanes 102 and the stationary vanes 123 to be transferred to the base portion 129. The exhaust gas transferred to the base portion 129 is sent to the exhaust port 133 while being guided by the thread grooves 131a of the threaded spacer 131.
In the above-described example, the threaded spacer 131 is provided in the outer periphery of the rotary vane 102d, and the thread grooves 131a are formed in the inner peripheral surface of the threaded spacer 131. However, conversely to the above, the thread grooves may be formed in the outer peripheral surface of the rotary vane 102d, and a spacer with a cylindrical inner peripheral surface may be arranged in the periphery thereof.
Further, in order that the gas sucked in through the inlet port 101 may not enter the electrical section formed of the motor 121, the lower radial electromagnets 105, the lower radial sensors 108, the upper radial electromagnets 104, the upper radial sensors 107, etc., a predetermined pressure is maintained with a purge gas.
For this purpose, piping (not shown) is arranged in the base portion 129, and the purge gas is introduced through the piping. The purge gas thus introduced flows through the gaps between a protective bearing 120 and the rotor shaft 113, between a rotor and stator of the motor 121, and between a stator column 122 and the rotary vanes 102 before being transmitted to the exhaust port 133.
While the turbo molecular pump main body 100 and the control device 200 are usually formed as separate components, they are, in some cases, integrated with each other for a space saving as shown in JP 10-103288 A and JP 11-173293 A.
FIG. 6 shows an example in which the turbo molecular pump main body 100 and the control device 200 are not separated but integrated with each other. In this case, cables 161 are attached to the connector 160 on the turbo molecular pump main body 100 side. A connector 260 is arranged at the other end of the cables 161 so as to be detachable with respect to the control device 200. The connector 160 and the connector 260 respectively protrude from the side portion of the turbo molecular pump main body 100 and the control device 200, with the cables in a bundle extending between the connectors.
In a 5-axis control magnetic bearing, the number of cables is 30 or more, so a large size vacuum connector is required. The cables are thick, and their bending radius is large. However, they are flexible to a certain degree, so they are not easily damaged or the like by an excessive force applied at the time of assembly. On the other hand, they involve a problem in terms of space.
In another example of the arrangement in which the turbo molecular pump main body and the control device are integrated with each other, instead of exposing the cables out side the turbo molecular pump main body 100 and the control device 200 as shown in FIG. 6, it is possible, as shown in FIG. 7, to directly connect a male connector 165 protruding from a turbo molecular pump main body 110 with a female connector 265 protruding from a control device 210.
In this connection, the male connector 165 is a vacuum connector, and is fastened to the turbo molecular pump main body 110 by bolts 167. The female connector 265 is similarly fastened to the control device 210 by bolts 169. Further, a plurality of spacers 171 are provided between the turbo molecular pump main body 110 and the control device 210. The spacers 171 are formed as hollow cylinders, and bolts 173 are passed through them so as to fix the turbo molecular pump main body 110 and the control device 210 to each other through the intermediation of the spacers 171.
In this way, the male connector 165 is fastened to the turbo molecular pump main body 110 by the bolts, and the female connector 265 is fastened to the control device 210 by the bolts, so, when, for example, the control device 210 is inserted obliquely to attach it to the turbo molecular pump main body 110, an excessive force maybe exerted between the male connector 165 and the female connector 265, resulting in damage of the connectors.